Switch contact



'Aug. 23, 1966 L. MANCINI 3,268,851

SWITCH CONTACT Filed March 5, 1964 2 Sheets-Sheet l 1NVE NT OR. A [4 d Ala/701221.

L. MAN ClNl SWITCH CONTACT Aug. 23, 1966 2 Sheets-Sheet 2 Filed March 5, 1964 INVENIOR' 1 47 Mdflc'z 21a E nTToJFAEYs.

United States Patent This invention relates to switch contacts and to a method of making the same, and has particular reference to a new and improved dry reed switch disconnect adapted to be soldered to a circuit board or the like.

In dip soldering where the dipping operation is prolonged, the molten solder tends to flow through the eyelet portion of the terminal and wet the contact area. According to the present invention, this difiiculty is overcome by incorporating in the terminal a core of heat resistant material, such as Teflon, which protects the contact area from molten solder even when the dipping operation is carried out at a temperature as high as 800 F. and for a time up to ten seconds.

A principal object of the invention, therefore, is to provide a new and improved switch contact adapted to be soldered to a circuit board or the like.

Other and further objects of the invention will be apparent from the following description and claims and may be understood by reference to the accompanying drawings, of which there are two sheets, which by way of illustration show a preferred embodiment of the invention and what I now consider to be the best mode of applying the principles thereof. Other embodiments of the invention may be used without departing from the scope of the present invention as set forth in the appended claims.

In the drawings:

FIG. 1 is a perspective view of a contact embodying the invention before it is separated from the strip from which it is formed;

FIG. 2 is an enlarged sectional view taken along the line 22 of FIG. 1;

FIG. 3 is an enlarged sectional view taken along the line 33 of FIG. 1;

FIG. 4 is an end elevational view of the contact;

FIG. 5 is a perspective view illustrating the assembly of the contact to a circuit board before the solder dipping operation;

FIG. 6 is a view illustrating several steps in the method of making the terminal; and

FIGS. 7 and 8 are perspective views illustrating the manner in which the core of heat resistant material is incorporated in the eyelet portion of the contact.

As illustrated in FIGS. 1 to 5, the contact indicated generally at 20 provides a terminal which is adapted to be mounted in a hole in a circuit board, as illustrated in FIG. 5. The terminal includes an eyelet or tubular supporting plug or barrel 22 at one end and an integral contact indicated generally at 24 at the other end. The eyelet comprises a rolled-up sheet metal blank 26 (FIG. 6), and the contact as illustrated comprises spaced blade type spring contact elements 28 and 30 which are arranged for receiving and frictionally holding a current conductor therebetween. A core 32 of heat resistant material, such as Teflon, copper or brass, is tightly fitted in the eyelet portion 22. The eyelet portion 22 terminates at its lead end in a frust-o-conical portion 34. An inwardly extending tab 36 is positioned intermediate the ends of the contact and adjacent the inner end of the core 32. To prevent displacement of the core, the tubular portion 22 may be provided with one or more tangs 38 which are adapted to penetrate the core for locating the same against axial movement. Externally the terminal may be provided with one or more transverse shoulders 40 which face 3,268,851 Patented August 23, 1966 ice away from the lead end of the plug and form an abutment for an inserting tool to expedite insertion of the eyelet portion 22 into the hole in the circuit board. The contact may be made out of bronze strip stock A hard, and the terminal preferably is tin electroplated after the stamping operation.

The terminals may be made in strip form as illustrated in FIG. 6 in which a series of blanks are left attached to a connecting strip 42. Each of the blanks is rolled up to form a contact, as illustrated in FIG. 1, and with the core 32 inserted in the eyelet portion 22 in the manner illustrated in FIGS. 7 and 8. As there shown, after the blank for each terminal is shaped in the form of a U in cross section, that is, partially rolled up, a rod or wire 44 of core stock is fed to a cutter indicated generally at 46. The blade 48 of the cutter is operable to sever the lead end of the rod 44 to form a core 32 which is then positioned in the open eyelet as illustrated in FIG. 8. The cutter 46 is positioned directly above the station at which the open eyelet is presented, as shown in FIG. 7, so that when the lead end of the rod is severed it will fall into the eyelet portion of the contact. However, any suitable means may be provided for insuring the proper positioning of the core 32 in the open eyelet.

The tab 36 forms an abutment for locating one end of the core 32, although this may be dispensed with since when the eyelet is closed the core 32 is compressed therein. Any suitable means may be provided for closing the eyelet portion of the contact after the insertion of the core therein and for providing the lead end of the contact with the frusto-conical portion 34 as shown in FIG. 1.

The contacts preferably are left connected to the strip 42 until they are about to be inserted by a suitable applicator into the hole in the circuit board, when the contacts may be individually separated from the connecting strip 42.

In closing the eyelet around the core 32, the diameter of the Teflon wire may be reduced as much as 20% to 25%, thus providing a tight fit between the core 32 and the inside of the eyelet bar-rel and eliminating any capillary passages through which solder might flow. After the closing of the eyelet barrel the terminal is electroplated. The Teflon wire may be stripped from the spool and fed directly to the cutter 46, by any conventional feed which will feed the rod 44 a given amount when the cutter blade 48 is retracted.

While I have illustrated and described a preferred embodiment of my invention, it is understood that this is capable of modification and I therefore do not wish to be limited to the precise details set forth but desire to avail myself of such changes and alterations as fall within the purview of the following claims.

I claim:

1. A switch contact terminal adapted to be mounted in a hole in a circuit board, said terminal including a tubular supporting plug on one end for insertion in such hole and an integral contact at the other end, said plug comprising a rolled up sheet metal blank forming a tubular portion, said plug when positioned in the circuit board hole being adapted to form a part of a solder system which includes a circuit element on said board, said contact comprising blade type spring contact elements projecting from one end of said hollow tubular portion, a core of'heat resistant material tightly fitted in said hollow tubular portion so as to prevent wicking of the solder through said tubular portion when it and the board are solder dipped, said hollow tubular portion terminating at its lead end in a frusto-conical portion and having an inwardly extending tab at its other end positioned adjacent to the end of said core, said tubular portion having indentations embedded in said core and external transverse shoulders facing away from the lead end of said plug.

2. A switch contact terminal according to claim 1 wherein said core is formed of a plastic material of the Teflon type.

3. A switch contact terminal adapted to be mounted in a hole in a circuit board, said terminal including a tubular supporting plug on one end for insertion in such hole and an integral contact at the other end, said plug comprising a rolled up sheet metal blank forming a tubular portion, said plug when positioned in the circuit board hole being adapted to form a part of a solder system which includes a circuit element on said board, and a core of heat resistant material tightly fitted in said hollow tubular portion so as to prevent wicking of the solder through said tubular portion when it and the board are solder-dipped, said hollow tubular portion terminating at its lead end in a frusto-conical portion and having an inwardly extending tab at its other end, said core being confined within said plug between said frustoconical portion and said tab.

4. A switch contact terminal adapted to be mounted in a hole in a circuit board, said terminal including a tubular supporting plug on one end for insertion in such hole and an integral contact at the other end, said plug forming a tubular portion, said plug when positioned in the circuit board hole being adapted to form a part of a solder system which includes a circuit element on said board, said contact comprising spring contact elements projecting from one end of said hollow tubular portion 30 and adapted for receiving and holding a current conductor therebetween, a core of heat resistant material tightly fitted in said hollow tubular portion so as to prevent wicking of the solder through said tubular portion when it and the board are solder-dipped, said hollow tubular portion terminating at its lead end in a frusto-conical portion and having an inwardly extending tab at its other end positioned adjacent to the end of said core and external transverse shoulders facing away from the lead end of said plug, said core being positioned within said plug between said frusto-conical portion and said tab.

References Cited by the Examiner UNITED STATES PATENTS 2,689,337 9/1954 Burtt et al. 339-275 X 2,691,771 10/1954 Burtt et al. 339-275 X 2,822,529 2/1958 Heath 339-258 2,866,171 12/1958 Wagner ct al. 339-275 X 3,083,351 3/1963 Nielsen 339-258 X 3,116,101 12/1963 Kikta 339-258 3,121,602 2/1964 Tuchel 339-275 3,192,610 7/1965 Keating 29-15555 3,203,078 8/1965 Ustin 29155.55

FOREIGN PATENTS 1,309,299 10/1962 France.

EDWARD C. ALLEN, Primary Examiner.

PATRICK A. CLIFFORD, Examiner.

P. TEITELBAUM, Assistant Examiner. 

3. A SWITCH CONTACT TERMINAL ADAPTED TO BE MOUNTED IN A HOLE IN A CIRCUIT BOARD, SAID TERMINAL INCLUDING A TUBULAR SUPPORTING PLUG ON ONE END FOR INSERTION IN SUCH HOLE AND INTEGRAL CONTACT AT THE OTHER END, SAID PLUG COMPRISING A ROLLER UP SHEET METAL BLANK FORMING A TUBULAR PORTION, SAID PLUG WHEN POSITIONED IN THE CIRCIUT BOARD HOLE BEING ADAPTED TO FORM A PART OF A SOLDER SYSTEM WHICH INCLUDES A CIRCUIT ELEMENT ON SAID BOARD, AND A CORE OF HEAT RESISTANT MATERIAL TIGHTLY FITTED IN SAID HOLLOW TUBULAR PORTION SO AS TO PREVENT WICKING OF THE SOLDER THROUGH SAID TUBULAR PORTION WHEN IT AN THE BOARD ARE SOLDER-DIPPED, SAID HOLLOW TUBULAR PORTION TERMINATING AT ITS LEAD END IN A FRUSTO-CONICAL PORTION AND HAVING AN INWARDLY EXTENDING TAB AT ITS OTHER END, SAID CORE BEING CONFINED WITH SAID PLUG BETWEEN SAID FRUSTOCONICAL PORTION AND SAID TAB. 